This invention relates to a recording/playback apparatus, a recording/playback method and a presentation medium. In particular, the present invention relates to a recording/playback apparatus capable of recording and playing back data with a high degree of efficiency by modifying the number of retries.
Data recorded or played back by a hard disc drive (abbreviated hereafter to an HDD) is controlled by a file v management function of an operating system (abbreviated hereafter to an OS) which runs on a host computer. For example, the HDD is not aware of a location or a free area into which data is to be recorded, so that, in a recording operation, data is written into a location specified by the host computer. In a playback operation, on the other hand, data recorded on a disc is read out from a location specified by the host computer.
In the case of such an OS as MS-DOS(trademark) and UNIX(trademark), a recording area of a disc is divided into data blocks or sectors each having a fixed size of 512 or 1,024 bytes during initialization. Data is recorded in data-block units. This method is referred to as a fixed-size division method.
In the case of the fixed-size division method, when a disc is initialized, a sector specific number, which is also referred to as a sector ID, is written into the beginning of a sector. A sector ID represents a physical location on a disc. Typically, a sector ID comprises an 8-bit sector number, a 16-bit track number, an 8-bit surface number and a 16-bit error-inspection code which is referred to hereafter as a CRC (Cyclic Redundancy Check) code.
The host computer controls sector IDs as a series of logical block addresses (LBAs). In an operation to record data, the host computer specifies an LBA representing a physical location on the disc into which the data is to be written.
FIG. 10 is a block diagram showing a typical configuration of the related art HDD. Assume that MS-DOS is used as an OS in this typical configuration. In the HDD 1, a microprocessor unit (abbreviated hereafter to an MPU, Micro Processing Unit) 11 controls all functions of the HDD 1. A servo circuit 12 generates a driving signal for controlling a voice coil motor (abbreviated hereafter to VCM) 13. The VCM 13 moves a magnetic head (not shown) to a predetermined track position on a disc 18. A buffer 16 is used for storing data received from an external source and data to be supplied to an external destination. A read/write channel processing unit 17 carries out processing to generate a signal to be recorded onto the disc 18 and processing to play back a signal read out from the disc 18. Controlled by the MPU 11, a hard-disc controller (abbreviated hereafter to an HDC) 15 controls operations to write and read out data into and from the buffer 16 and exchanges data with the R/W channel processing unit 17. The MPU 11, the servo circuit 12, the HDC 15 and the R/W channel processing unit 17 are connected to each other by an MPU bus 14.
ECCs (Error Correction Codes) are added to data to be recorded onto the disc 18. When an ECC error is detected for a sector in an operation to play back data from the sector, the MPU 11 issues a command to repeat the operation to read out data from the sector. This repeated operation is called as a retry. In an ordinary HDD, a number of retries are allowed and performed internally.
In a case where data can not be read out correctly from a sector, even if a number of allowable retries have been carried out, the MPU 11 treats the sector as a defective sector. In a following operation to write data into a defective sector, the data is written into a sector in an alternate area. This is called alternative-sector processing.
The HDD 1 is connected to the host computer 2 by a bus, such as an SCSI (Small Computer System Interface) bus or an IDE (Intelligent Drive Electronics) bus.
In the host computer 2, MS-DOS is used as an OS 21. A disc driver 22 is a program which allows the disc 18 to be accessed as a block device. A logical format program 23 is a program for writing necessary initialization information such as sector IDs and a file management table during initialization of the disc 18. Linked to the device driver 22 and the logical format program 23, a BIOS (Basic Input Output System) 24 renders I/O (Input/Output) services for inputting and outputting data from and to the HDD 1. The BIOS 24 can be regarded as a collection of routine programs dependent on hardware.
When data having a high rate such as AV (audio/video) data is recorded or edited on the HDD 1 in logical block units, the continuous data is scattered over the disc into small pieces of data. The scattering of data is known as fragmentation. When fragmented data is read out from a disc, the read operation frequently enters a wait state due to head seeks and disk revolutions to read target positions, breaking the continuity of the output data.
In order to solve this problem, data is recorded not in logical block units, but in cluster units each comprising several block units. Typically, the size of a cluster unit is 1,024 sectors. The size of a cluster unit is set at such a value that the continuity of output data in a playback operation is sustained, even if the data recorded on the disc is fragmented into cluster units.
The size of a cluster is made uniform for all data types in order to make operations to write and read out data easy to control. Typically, the size of a cluster is set at an extremely small value which is obtained with regular data such as text data taken as a reference. If the size of a cluster is too small, however, data recorded on the disc is prone to fragmentation described above. If a small amount of data is recorded in large cluster units, an excessively large recording area will be wasted.
The size of a cluster can also be determined from a simple proportional relation with a reference data transfer rate or an assumed transfer-channel count. In this case, however, the size of a cluster is not optimum. In addition, the type of data and the number of transfer channels are not reflected in an upper limit of the number of retries that can be carried out in the event of an error detected in a data recording or playback operation. As a result, the transfer rate is not guaranteed for data with a strict continuity requirement such as AV data.
It is thus an object of the present invention to provide a recording/playback apparatus and a recording/playback method wherein the number of retry operations is determined in accordance with the size of each of units in which data is written and/or read out so that the data can be recorded and/or played back with a high degree of efficiency without losing data continuity.
In order to attain the above objects, according to a first aspect of the present invention, there is provided recording/playback apparatus, a recording/playback method and a presentation medium. The apparatus comprises a supplying device for supplying the continuous data at a predetermined transfer rate, a recording device having a certain seek performance and recording mode for recording the continuous data on the recording medium in recording unit, and a first setting device for setting the size of the recording unit according to the transfer rate of the supplied continuous data. The first setting device sets the size of the recording unit according to the seek performance of the recording device. The recording device includes a designating device for designating the transfer rate according to recording mode. The first setting device includes a device for setting the recording unit size according to the recording mode. The apparatus further comprises a second setting device for setting the number of allowable retries according to the transfer rate. The apparatus further comprises a second setting device for setting the number of allowable retries according to the seek performance. The apparatus further comprises a second setting device for setting the number of allowable retries according to the recording unit size.